The use of electric lift actuators is well-known in the materials handling industry. Electric lifts are particularly useful, and have been applied in several embodiments to provide varying lift capabilities for personal lift devices for lifting and transporting loads. Examples of such devices include the Gorbel G-Force™ and Easy Arm™ systems.
More specifically, the present invention is directed to a class of material handling devices called balancers or lifts, which include a motorized lift pulley having a cable or line which, with one end fixed to the pulley, wraps around the pulley as the pulley is rotated, and an end-effector or operator control in the form of a pendant or similar electromechanical device that may be attached to the other (free or non-fixed) end of the cable. The end-effector has components that connect to the load being lifted, and the pulley's rotation winds or unwinds the line and causes the end-effector to lift or lower the load connected to it. In one mode of operation, the actuator applies torque to the pulley and generates an upward line force that exactly equals the gravity force of the object being lifted so that the tension in the line essentially balances the object's weight. Therefore, the only force the operator must impose to maneuver the object is the object's acceleration force.
In one class of systems, these devices measure the human force or motion and, based on this measurement, vary the speed or force applied by the actuator (pneumatic drive or electric drive). An example of such a device is U.S. Pat. No. 4,917,360 to Yasuhiro Kojima, U.S. Pat. No. 6,622,990 to Kazerooni, and U.S. Pat. No. 6,386,513 to Kazerooni. U.S. Pat. No. 6,622,990 for a “HUMAN POWER AMPLIFIER FOR LIFTING LOAD WITH SLACK PREVENTION APPARATUS,” to Kazerooni., issued Sep. 23, 2003, is hereby incorporated by reference in its entirety. With this and with similar devices, when the human pushes upward on the end-effector the pulley turns and lifts the load; and when the human pushes downward on the end-effector, the pulley turns in the opposite direction and lowers the load. Similar operation may be observed in systems having what is frequently referred to as a “float mode” wherein an operator's application of upward or downward force to the load itself results in system-assisted movement of the load.
The embodiments disclosed herein are designed to provide several improvements to existing electric actuator and lift systems. In a general sense, the improved design facilitates the standardization of the actuator design in order to reduce the number of components required to manufacture and service a broad range of lift systems, whereby fewer components are changed between several actuators having varying load-lifting ranges. The redesign also modifies several components in the actuator and the associated user controls (e.g., operator control pendant) so as to improve the reliability, serviceability and expandability of the controls.
Disclosed in embodiments herein is a lift actuator, comprising: a controller; an electrical motor for driving the actuator, said motor operating in response to control signals from the controller, to rotate a drum upon which a wire rope, with one end fixed to the drum, is wound and unwound; and an operator interface, attached near the free end of the wire rope, said operator interface including a detachable lifting tool, wherein the operator interface provides signals from the operator to the controller to control the operation of the actuator.
Also disclosed are: a frame for rotatably suspending the motor, mechanical reduction and drum therefrom; a load sensor attached to the frame, for sensing the load as a result of rotation of the motor/reducer/drum assembly when a load is applied to the unwound end of the wire rope; a slack sensor for sensing the angle of orientation of the motor/reducer/drum assembly and determining when a slack condition is present in response to a signal from the slack sensor, mounted on the rotating assembly in one embodiment; a universal motor and reducer assembly that may be fitted with one of a plurality of additional reducers in order to alter the capacity range of the actuator; a planetary reducer, wherein the mechanical configuration of the reducer is substantially enclosed within the wire rope pulley drum; a cable guide for controlling the position and maintaining the wrap integrity (tightness) of the cable upon being wound upon or unwound from the drum; adjustable cable limit sensors, triggered in response to the extreme axial movement of the cable guide as the cable is wound and unwound; and the cable guide including a plurality of threads for mating with grooves on the drum to provide the lateral force to move the guide as the cable is wound and unwound. Said grooves also serve as location for the wire rope on the drum, yielding precise, single layer placement of the wire rope on the drum.
Further disclosed relative to various alternative embodiments of the operator interface are: a handle; a pivotable coupling for attaching the interface to the wire rope, but permitting 360-degree rotation thereof relative to the rope by way of a pancake-like slip ring suitable for providing electrical contacts and an air channel or conduit therewith; a coil sensor for sensing a vertical component of a displacement applied to the handle, wherein the handle is coupled to a core passing within the coil by a flexible filament; a liquid crystal display on the interface to display status information to an operator; a non-contact, optical proximity sensor for detecting the presence of an operator's hand on the handle during operation; and a quick-disconnect, bayonet-type or pin-type attachment for tools to be attached to the bottom of the interface.